The present invention relates to fixturing systems for clamping a workpiece during machining in general. In particular it concerns a fixturing device for use in universal modular fixturing systems for clamping a variety of workpieces during grinding, milling, boring or other machining procedures.
Conventional fixturing requires the design and production of a fixture specific to any given workpiece and is therefore time consuming and expensive. The combined labor of design and production for a typical fixture may take a technician as much as a hundred hours. The expenses of such work may be feasible for large scale manufacture, but are often prohibitive for smaller scale applications.
In an attempt to reduce production time and costs a number of modular fixturing systems have been developed. These modular fixturing systems generally have a flat base plate with a variety of attachable supporting elements and clamping elements. By building up different combinations of the elements it is possible to produce fixtures to support a range of different workpieces.
Modular fixturing systems are generally of one of two types or a combination thereof. One type uses a base plate drilled with a matrix of accurately positioned holes. This enables precise and repeatable positioning of supporting and clamping elements. Systems of this type are commercially available from ERON and CARR LANE.
The other type of modular fixturing system is the slotted grid system in which the supporting and clamping elements slide into T-shaped slots and are tightened by means of bolts to grip the recessed surfaces of the slots. Systems of this type are commercially available from HALDER and KUIKKA.
Use of the modular systems currently available is limited to a relatively small proportion of workpieces. One reason for the limited application of such systems is that fixture design is restricted by the fixed pitch between the holes or slots and many workpieces may need supporting or clamping at intermediate positions. In particular, in the systems based on a matrix of accurately positioned holes, the design is limited by the position of the holes. The holes commonly form a matrix with a pitch of 30 mm. alternating between threaded bores and locating bores. The effective pitch between similar bores is therefore 60 mm.
A further shortcoming of the existing systems has become highly significant in the light of recent developments in machining methods. The development of machining centers and various types of numerical control machines has enabled multiple processes to be performed consecutively. To do this, however, all the surfaces of the workpiece which are to be processed must be sufficiently accessible. When modular fixturing systems are used, the combination of a base plate with sufficient supporting and clamping elements attached to its face in most cases greatly limits access to the workpiece, preventing machining of multiple parts in one position.
A further shortcoming of the existing systems is the specificity of each configuration. Although the individual components are all reusable, in most cases the system needs to be completely dissembled and redesigned for each new application, often requiring a mainly new group of components. Thus time savings over conventional fixturing are not so great and a sufficient system to cover a range of applications may require many parts making it very expensive.
There is therefore a need for increased applicability of modular fixturing systems, as well as a reduction in their costs. There is also a need for modular fixturing systems which offer continuous adjustability, increased access to the workpiece and require fewer parts than the existing systems.